Download the HMRC app.
HMRC has released an official app for iOS and Android devices that allows users to manage their tax, National Insurance, and benefit information. Individuals can use the app to update personal details, check tax codes, view Self Assessment information, and make payments. Users can sign in using their existing HMRC online service credentials or create new ones directly within the app.
Source: https://www.gov.uk/guidance/download-the-hmrc-app. Summarised automatically from the official source — general information, not advice.